1. Field of the Invention
This invention generally relates to humidifiers and more specifically to humidifiers that boil water as a part of a humidification by vaporization process.
2. Description of Related Art
The most common known means for humidifying rooms is a vaporizer that includes a water tank and an immersed spaced electrode assembly. With water in the water tank, voltage is applied to the spaced electrodes. If the water has electrolytic properties, a current passes between the electrodes and generates heat bringing to a boil water proximate the electrodes. Boiling vaporizes the water into steam that rises to the surface of the water and by normal thermal convection through an output port to outside air.
Such humidifiers generally are inefficient particularly as the vaporization rate decreases over time. Vaporization rate is a function of the conductivity of the water and the water level in the water tank. In some cases it becomes necessary to add an electrolyte, such as salt or baking soda, to promote conductivity to achieve adequate quantities of steam. As the water level in a water tank decreases, the effective heating area between the electrodes decreases reducing the vaporization rate. The boiling process acts as a distilling process and leaves deposits on the electrodes that also reduce the vaporization rate.
At the output from such a humidifier the steam is at an elevated temperature near the 100xc2x0 C. boiling point temperature. Steam at this temperature can present a hazard if it contacts an individual. Over time the boiling process produces water circulation and elevates the temperature of all the water in the tank and the temperature of the water tank itself. Further, the assembly typically is held in place by gravity. If the humidifier is accidentally tipped, there is nothing to prevent all the heated water from spilling. It also becomes easy for someone to remove the cover with its electrodes during use thereby to pose a risk of electric shock if the electrodes are touched.
In order to overcome some of these disadvantages, a number of suggestions have been made for alternate designs. For example, it has been suggested to combine an immersible, self-contained heater with a fan for ejecting steam generated by the heating element with an air mixture. U.S. Pat. No. 3,809,374 (1974) to Schossow discloses one such humidifier having a small insulated vaporization chamber located centrally in a water tank or storage chamber with an electrically operated heater that heats water within the vaporization chamber. A fan above the chamber draws air and steam from the vaporization chamber and then expels it through an output port.
U.S. Pat. No. 4,155,001 (1979) to Schossow discloses another humidifier using an electrode type steam generator structure. A tubular member defines a boiling chamber and a pair of concentric electrodes define an area for boiling water.
U.S. Pat. No. 5,611,967 (1997) to Jane et al. discloses humidifier that has an evaporative cavity and a warm mist vaporization cavity. A selectively operable heating element is disposed within the warm mist cavity to vaporize liquid in that cavity. The resulting liquid vapor is discharged from a warm mist chamber into a surrounding element. In a combination evaporative/warm mist mode a fan induces further motion.
Each of these references discloses a system that overcomes some but not all the disadvantages of the original electrode-type humidifiers. The Schossow-374 patent provides an independent heater that is not dependent upon the electrolytic characteristics of the water, but requires the addition of a fan in order to effectively produce a warm mist. The Schossow-001 patent also requires a fan and utilizes the characteristic of water conductivity in order to achieve evaporation or boiling. The Jane patent discloses a vaporization system in which steam rises through a nozzle or vapor discharge tube to mix with air to the exterior of the vaporizer.
Other modifications to vaporizers have also been proposed that do not rely on a fan. For example, U.S. Pat. No. 5,247,604 (1993) to Chiu discloses a humidifier with a base that includes a liquid reservoir and a humidification mechanism that dispenses liquid contained in the reservoir. The reservoir includes a boiler cavity and a liquid supply channel between the boiler cavity and a supply tank. Water passes to the boiler cavity to be vaporized with the resulting steam rising through a nozzle that includes an open top and a well for receiving a medicant. As steam rises through the channel it heats any material in the medicant well. Steam then mixes with air after it leaves the channel.
In U.S. Pat. No. 5,343,551 (1994) to Glucksman an immersible heater boils water in a boiling or evaporation chamber. Steam generated during the boiling operation passes through a single nozzle and is directed into a vertical channel. As the steam accelerates passing through the nozzle, it produces an area of low pressure upstream of the tube. The tube is disposed in a chamber with opening to receive exterior air. Consequently combined air and steam pass through the tube and are exhausted exteriorly of the housing.
Each of these patents discloses particular features that represent improvements over original electrode-type vaporizers. However, each still has certain disadvantages. For example, the Glucksman patent discloses internal mixing of air and steam through a single nozzle. However, the resulting distribution of the mixture of air and steam is not even. Whereas the Chiu patent discloses a method of warming a medicant in order to promote dispersal of the medicant, no such structure is shown in the Glucksman patent. Notwithstanding these particular proposals, there still remains a significant bias toward using the conventional vaporizer with the spaced electrodes.
Therefore it is an object of this invention to provide a humidifier that supplies a mixture of air and water vapor in a warm mist.
Therefore it is an object of this invention to provide a humidifier that supplies warm mist with an even distribution of water vapor and air in the warm mist.
Yet another object of this invention is to provide a humidifier that produces a warm mist and an entrained medicant.
Still yet another object of this invention is to provide a humidifier that maintains a substantially constant vaporization rate.
Yet still another object of this invention is to provide a humidifier that includes an internal boiling chamber that allows water in a surrounding tank to remain at essentially room temperature.
In accordance with this invention, a humidifier includes an open top water tank for storing water. The water tank supports a warm mist distributor with a mixing chamber proximate the open top. A vaporization module in the water tank depends from the warm mist distributor. The vaporization module includes a boiling chamber with a heater. A plurality of nozzles direct steam from the boiling chamber to the mixing chamber thereby to produce a warm mist output.